MDN Web Docs focuses on the basics of HTML, CSS and JavaScript, among other aspects of web design, and has a learning pathway for aspiring front-end web developers.

Designer/developer Shay Howe put together a set of free lessons to help you learn the basics of HTML and CSS as well as more advanced techniques to improve your abilities.

In this beginner-level course, students learn HTML basics, including tags and tables, forms and elements. Learn Java Time to Completion: 25 hours Course Format: Self-paced ...

Although Google recently discontinued its free Grasshopper app for teaching the basics, you can find plenty of tutorials and guides for learning coding fundamentals on your phone.